Conjugated organic molecules excitation

The de-excitation path available to conjugated organic molecules is controlled by quantum-mechanical rules which are complex. Some molecules will relax spontaneously, other will not (within a reasonable time) without assistance from another material/mechanism. The presence of Oxygen is a special case. Resonant conjugated molecules with two Oxygen atoms will not fluoresce and there only means of de-excitation is by means of a direct transition that is not allowed because of the presence of the triplet state. The nonresonant conjugates normally de-excite thermally via a two-step process. 

Using the INDO Cl procedure, the excitation energies of the Sj, Tj, and quintet (Q,) states for 46 conjugated organic molecules have been calcu-lated. " It is concluded that quintet states are accessible in many cases through triplet-triplet annihilation. Delayed-fluorescence o.d.m.r. and e.p.r. studies of... 

As it was mentioned in the Introduction, in contrast to the extensive investigations on the solvent influence on the molecular (hyper)polarizabilites, there are only few theoretical works on the TPA cross section (S) of the donor-acceptor TT-conjugated organic molecules in which TPA from the ground to the CT excited state is considered. Below, we give short review of these works. 

In this review, we explain the SAC-CI applications to molecular spectroscopy with some examples. In Section 2, we briefly explain the theoretical and computational aspects of the SAC-CI method. Then, we show some SAC-CI applications to molecular spectroscopy the excitation and ionization spectra of tt-conjugated organic molecules (Section 3), collision-induced absorption spectra of van der Waals complex (Section 4), excitation spectra and NMR chemical shifts of transition metal complexes (Section 5), photofragmentation reaction of Ni(CO)4 (Section 6), absorption spectrum of free-base phthalocyanine (FBPc) and bacterial photosynthetic reaction center... 

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